Re: [Qemu-devel] [PATCH 1/7] block: only force IO completion in .bdrv_truncate if we are shrinking

[Kevin Wolf]

Am 07.03.2013 um 10:16 hat Peter Lieven geschrieben:
> >> If bs->growable is 1 for all drivers, whats the fix status of 
> >> CVE-2008-0928? This
> >> flag was introduced as a fix for this problem.
> >> 
> >> bdrv_check_byte_request() does nothing useful if bs->growable is 1.
> > 
> > Don't ignore the difference between bdrv_open() and bdrv_file_open().
> > Typically you have two BDSes: On top there is e.g. a qcow2 BDS that is
> > opened through bdrv_open() and has bs->growable = false. Its bs->file is
> > using the file protocol (raw-posix driver) and opened by
> > bdrv_file_open(). This one has bs->file->growable = true so that qcow2
> > can write to newly allocated areas without calling bdrv_truncate()
> > first.
> 
> Sorry, I have to admin I am little confused by what is happening in 
> bdrv_open().
> 
> However, what I can say is that bs->growable is 1 for an iSCSI backed
> harddrive and I wonder how this can happen if bdrv_file_open is not used for
> opening it because that is the only place where bs->growable is set to 1.
> 
> cmdline:
> x86_64-softmmu/qemu-system-x86_64 -k de -enable-kvm -m 1024 -drive 
> if=virtio,file=iscsi://172.21.200.31/iqn.2001-05.com.equallogic:0-8a0906-16470e107-713001aa6de511e0-001-test/0
>  -vnc :1 -boot dc -monitor stdio

It is used for the iscsi driver. You have a raw BDS (growable == false)
on top of an iscsi one (growable == true).

Kevin